Syndiotactic polystyrene is a very attractive polymer. The polymer shows low specific gravity, low dielectric constant, high flexural modulus, good heat resistance, good rigidity, high melting point (Tm) of about 270° C. and excellent resistance to chemicals. Accordingly the syndiotactic polystyrene has become a promising material for various applications in the automotive, electronic and packaging industries. However, the applications of the syndiotactic polystyrene resin composition are highly limited because impact strength is too low. To overcome such shortcoming, an impact reinforcing material such as rubber and various compatibilizers for the syndiotactic polystyrene and the impact reinforcing material have been used in the syndiotactic polystyrene resin composition.
U.S. Pat. No. 5,270,353 to Nakano et al. discloses a styrene-based resin composition comprising a styrene-based polymer having a syndiotactic configuration and no functional group, a styrene-based polymer having an epoxy group and an inorganic filler surface treated by a silane compound or a titanium compound.
U.S. Pat. No. 5,352,727 to Okada discloses a polystyrene composition comprising syndiotactic polystyrene and a syndiotactic polystyrene impact modifier, said syndiotactic polystyrene impact modifier being the reaction product of a syndiotactic polystyrene having a first reactive functional group, and a rubbery elastomer containing a second reactive functional group, said first and second reactive functional groups being reactive with each other.
U.S. Pat. No. 5,391,603 to Wessel et al. discloses a composition comprising a syndiotactic, vinylaromatic thermopalstic resin, a rubbery, impact absorbing domain forming polymer, a nucleator for the syndiotactic, vinylaromatic thermoplastic resin, an mineral, glass, ceramic, polymeric or carbon reinforcing agent, and one or more polyarylene ethers or polar group modified polyarylene ethers.
U.S. Pat. No. 5,543,462 to Okada et al. discloses an impact resistant polystyrene composition comprising a styrenic polymer having syndiotactic configuration and a rubbery elastomer modified by a modifier having a polar group, and optionally a rubbery elastomer and/or a poly(phenylene ether).
U.S. Pat. No. 5,654,365 to Havriliak, Jr. et al. discloses a syndiotactic polystyrene composition impact-modified by a blend of polystyrene-hydrogenated polybutadiene block copolymers and one or more core/shell modifiers based on a lightly or non-crosslinked rubber core.
U.S. Pat. No. 5,760,105 to Okada et al. discloses a styrenic resin composition comprising an styrenic polymer having syndiotactic configuration (sPS) or modified sPS, a thermoplastic resin having a polar group, a rubbery elastomer having affinity for the sPS and a compatibilizer having a polar group.
U.S. Pat. No. 5,777,028 to Okada et al. discloses an impact resistant polystyrene composition comprising a styrenic polymer having syndiotactic configuration, a rubbery elastomer having an olefinic component or a polyolefin and a styrene/olefin block or graft copolymer having a microphase separation temperature of 180° C.
There are two major conventional methods to prepare a syndiotactic polystyrene composition. One is to improve elasticity of the syndiotactic polystyrene composition by simply blending a syndiotactic polystyrene and a rubber component, and the other is to improve surface properties between a syndiotactic polystyrene and a rubber component by using another rubber component as a compatibilizer to prevent phase separation at the surface. The latter method is more preferable in processability and physical properties. However, the latter method focuses on improvement of polarity of both the syndiotactic polystyrene and the rubber component but does not contribute improvement of impact strength to the syndiotactic polystyrene composition.
Accordingly, the present inventors have developed a syndiotactic polystyrene resin composition with good impact strength as well as good mechanical properties, in which a syndiotactic polystyrene-maleic anhydride (sPS-MA) and a hydrogenated styrene/butadiene/styrene-maleic anhydride (SEBS-MA) are employed as compatibilizers and a diamine compound is added as a coupling agent. The compatibilizers and coupling agent improve polarity of both the syndiotactic polystyrene and the rubber component and impact strength of the syndiotactic polystyrene composition.